These two formats are identical file formats. There is absolutely no difference between a .jpg image and a .jpeg image — they both use exactly the same JPEG compression algorithm and store image data in the same way.
The difference is only in the suffix, being a legacy issue from early computer history. The JPEG format was developed in 1992 by the Joint Photographic Experts Group. When Microsoft released early versions of Windows, the OS had a constraint: extensions were limited to be three characters long.
Which forced the 4-character .jpeg extension to be reduced to .jpg for Windows computers. Apple and Unix platforms, which never had the character limit, could use the longer .jpeg file extension from the beginning.
Even though both extensions work identically in nearly all current applications, there are specific scenarios where a service might need here the .jpeg file type. For these situations, changing the extension from .jpg to .jpeg is enough.
No actual file conversion is needed — only changing the extension solves the compatibility concern usually.
Use alljpgconverters.com providing completely free web-based JPG to JPEG converter without software needed.